ssh

ssh

sshd server

Set alternate port so the lazier script kiddies will pass you by

Port 12345

Determining ssh key metadata

Determining the fingerprint of an existing keyfile (bits, key type, encryption algorithm, etc)

ssh-keygen -l -f ~/.ssh/<file>

Example output

1024 SHA256:<my key> <username>@<hostname> (RSA)

ssh key forwarding

This is a handy feature that can store keys in a cache, including passphrases. For security reasons, it's best to set short expiration times on the keys in the agent.

Start the ssh-agent that will forward keys for you

Output looks like

SSH_AUTH_SOCK=/var/folders/zv/1s20m9ld4q3f9vbc8_p_tqsr0000gr/T//ssh-Q7NiRJVvk5X4/agent.7403; export SSH_AUTH_SOCK;
SSH_AGENT_PID=7404; export SSH_AGENT_PID;
echo Agent pid 7404;

Add any keys you want into the agent

ssh-add -t 86400 ~/.ssh/id_file_to_use #set expire time to 1 day

Output looks like

Enter passphrase for /your_home_dir/.ssh/id_file_to_use: 
Identity added: /your_home_dir/.ssh/id_file_to_use (/your_home_dir/.ssh/id_file_to_use) 
Lifetime set to 86400 seconds

If you see this error, something went wrong with setting the env var but it's easy to workaround

Could not open a connection to your authentication agent.

Workaround: Find the output from the agent startup and re-run these commands

SSH_AUTH_SOCK=original_output_value_here; 
export SSH_AUTH_SOCK;

and then retry the ssh-add command

ssh client

Config file

### Example entries

custom port

host server.org port 12345

public key authentication

host github.com IdentityFile /Users/jpinkham/.ssh/id_github_rsa PreferredAuthentications publickey

custom port + public key authentication

host my_local_server 192.168.1.161 port 123456 IdentityFile /Users/jpinkham/.ssh/id_file_here PreferredAuthentications publickey

```